1. Field of the Invention
This invention relates to water treatment, and more particularly concerns a method for the removal of dissolved ions from water employing a porous sponge material.
2. Description of the Prior Art
U.S. patent application Ser. No. 07/395,535, filed 08/18/89 discloses an open celled product useful in selectively abstracting dissolved ions from aqueous solutions. The product is comprised of a regenerated cellulose sponge and a water insoluble polymer durably associated with the cellulose. The polymer is essentially a polyethyleneimine (PEI) that has been insolubilized in a thermal curing step. The product finds use in removing trace quantities of toxic metals from industrial waste streams and naturally occurring waters such as acid mine drainage water.
U.S. patent application Ser. No. 07/561,006, filed 07/31/90 discloses a particularly preferred small cuboid configuration of the sponge product having a uniform distribution of polymer throughout the sponge and providing improved characteristics during manufacture and use. This product is particularly well suited for use in vertical columns wherein the water to be treated is passed through a bed comprised of a great multitude of the small cuboid sponges. It has been found however, that in such beds of sponges, leakage or "breakthrough" of metal ions sometimes occurs prematurely, namely before the sponge has become saturated with said ions. In instances where it is sought to separate pollutant metals from valuable metals such as gold, sharper separations are desirable.
It is accordingly an object of the present invention to improve the efficiency of utilization of ion-absorbing sponges.
It is another object of this invention to provide a method for increasing the amount of water that can be treated to acceptable specifications by a given quantity of ion-absorbing sponges.
It is a further object of the present invention to provide a method of the aforesaid nature for achieving sharper separation of dissolved gold from ions of base metals.
These objects and other objects and advantages of the invention will be apparent from the following description.